U.S. patent number 4,313,820 [Application Number 06/190,004] was granted by the patent office on 1982-02-02 for hydrodesulfurization of organic sulfur compounds and hydrogen sulfide removal with incompletely sulfided zinc titanate materials.
This patent grant is currently assigned to Phillips Petroleum Co.. Invention is credited to Floyd E. Farha, Jr., Lloyd E. Gardner.
United States Patent |
4,313,820 |
Farha, Jr. , et al. |
February 2, 1982 |
Hydrodesulfurization of organic sulfur compounds and hydrogen
sulfide removal with incompletely sulfided zinc titanate
materials
Abstract
Hydrogen sulfide is removed from a fluid stream by contacting
the fluid stream which contains hydrogen sulfide with an absorbing
composition comprising zinc, titanium and at least one promoter
selected from the group consisting of vanadium, chromium,
manganese, iron, cobalt, nickel, molybdenum, rhenium, and compounds
thereof. If organic sulfur compounds are present in the fluid
stream, the absorbing composition acts as a hydrodesulfurization
catalyst to convert the sulfur in the organic sulfur compounds to
hydrogen sulfide which is subsequently removed from the fluid
stream by the absorbing composition. If olefin contaminants are
present in the fluid stream, the absorbing composition acts as
hydrogenation catalyst to hydrogenate the olefin contaminants to
paraffins.
Inventors: |
Farha, Jr.; Floyd E.
(Bartlesville, OK), Gardner; Lloyd E. (Bartlesville,
OK) |
Assignee: |
Phillips Petroleum Co.
(Bartlesville, OK)
|
Family
ID: |
26823591 |
Appl.
No.: |
06/190,004 |
Filed: |
September 23, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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125438 |
Feb 28, 1980 |
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Current U.S.
Class: |
208/213; 208/145;
208/215; 208/216R; 423/230; 423/244.1; 502/38; 95/136 |
Current CPC
Class: |
B01J
23/16 (20130101); B01J 23/80 (20130101); C10G
45/10 (20130101); C10G 45/00 (20130101); C10G
45/04 (20130101); B01J 23/8873 (20130101) |
Current International
Class: |
B01J
23/16 (20060101); B01J 23/887 (20060101); B01J
23/80 (20060101); B01J 23/76 (20060101); C10G
45/10 (20060101); C10G 45/04 (20060101); C10G
45/02 (20060101); C10G 45/00 (20060101); C10G
045/04 (); C10G 045/60 () |
Field of
Search: |
;208/143,213,215,216R,217 ;210/683,669 ;423/230 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Berkman et al., Catalysts, Reinhold Pub. Corp., N. Y., (1940), p.
925. .
Carlisle et al., in J. Soc. Chem. Ind., vol. 57, (Oct. 1938), pp.
347-349..
|
Primary Examiner: Hearn; Brian E.
Parent Case Text
This application is a continuation-in-part of application Ser. No.
125,438, filed Feb. 28, 1980, now abandoned.
Claims
That which is claimed is:
1. A process for hydrodesulfurizing an organic sulfur compound
contained in a fluid stream to convert the sulfur in the organic
sulfur compound to hydrogen sulfide and for removing hydrogen
sulfide from the fluid stream comprising the step of contacting
said fluid stream under suitable hydrodesulfurization conditions
with an incompletely sulfided catalyst/absorbing composition
comprising zinc titanate, and at least one promoter selected from
the group consisting of vanadium, chromium, manganese, iron,
cobalt, nickel, molybdenum, rhenium, and compounds thereof, wherein
the concentration by weight of said at least one promoter in said
catalyst/absorbing composition is less than the total concentration
by weight of said zinc titanate in said catalyst/absorbing
composition.
2. A process in accordance with claim 1 wherein said organic sulfur
compound is selected from the group consisting of sulfides,
disulfides, mercaptans, carbonyl sulfide, thiophenes,
benzothiophenes, dibenzothiophenes and mixtures of any two or more
thereof.
3. A process in accordance with claim 1 wherein said fluid stream
contains an olefin contaminant which is hydrogenated when said
fluid stream is contacted with said catalyst/absorbing
composition.
4. A process in accordance with claim 3 wherein said fluid stream
is an aerosol propellant selected from the group consisting of
isobutane, n-butane, propane and mixtures of any two or more
thereof and said olefin contaminant is selected from the group
consisting of ethylene, propylene, n-butenes, isobutene, n-pentenes
and branched pentenes.
5. A process in accordance with claim 3 wherein said suitable
hydrodesulfurization conditions comprise a temperature in the range
of about 205.degree. C. to about 538.degree. C., a total system
pressure in the range of about 100 psig to about 1000 psig, a
hydrogen flow rate in the range of about 100 to about 10,000
SCF/bbl and a residence time for said liquid stream in the presence
of said catalyst/absorbing composition in the range of about 0.1 to
about 50 liquid volumes of said fluid stream per volume of said
catalyst/absorbing composition per hour.
6. A process in accordance with claim 3 wherein said suitable
hydrodesulfurization conditions comprise a temperature in the range
of about 260.degree. C. to about 427.degree. C., a total system
pressure in the range of about 100 psig to about 500 psig, a
hydrogen flow rate in the range of about 250 SCF/bbl to about 3,000
SCF/bbl and a residence time for said fluid stream in the presence
of said catalyst/absorbing composition in the range of about 1 to
about 20 liquid volumes of said fluid stream per volume of said
catalyst/absorbing composition per hour.
7. A process in accordance with claim 1 wherein said zinc titanate
is prepared by calcining a mixture of zinc oxide and titanium
dioxide in the presence of molecular oxygen at a temperature in the
range of about 650.degree. C. to about 1050.degree. C.
8. A process in accordance with claim 7 wherein the atomic ratio of
zinc to titanium in said catalyst/absorbing composition is in the
range of about 1:1 to about 3:1.
9. A process in accordance with claim 7 wherein the atomic ratio of
zinc to titanium in said catalyst/absorbing composition is in the
range of about 1.8:1 to about 2.2:1.
10. A process in accordance with claim 7 wherein said
catalyst/absorbing composition has been calcined in the presence of
molecular oxygen at a temperature in the range of about 500.degree.
to about 650.degree. C. after said at least one promotor has been
added to said zinc titanate.
11. A process in accordance with claim 10 wherein the concentration
of vanadium, chromium, manganese, iron, cobalt, nickel, or
molybdenum as individual promoters, if present, expressed as an
element, is in the range of about 0.4 to about 16 weight percent
based on the weight of said catalyst/absorbing composition and the
concentration of rhenium as an individual promoter, if present,
expressed as an element, is in the range of about 0.05 to about 2.5
weight percent based on the weight of said catalyst/absorbing
composition.
12. A process in accordance with claim 11 wherein the total
concentration of any combination of the group from which said at
least one promoter is selected, expressed as an element, is in the
range of about 1 to about 28 weight percent based on the weight of
said catalyst/absorbing composition.
13. A process in accordance with claim 1 wherein said at least one
promoter is the combination of cobalt and molybdenum.
14. A process in accordance with claim 11 wherein the
cobalt:molybdenum atomic ratio in said catalyst/absorbing
composition is in the range of about 0.3:1 to about 0.8:1.
15. A process in accordance with claim 1 wherein said
catalyst/absorbing composition additionally comprises at least one
oxidation promoter selected from the group consisting of ruthenium,
rhodium, palladium, silver, tungsten, iridium, platinum, and
compounds thereof.
16. A process in accordance with claim 15 wherein the concentration
of ruthenium, rodium, palladium, silver, iridium or platinum as
individual oxidation promoters, expressed as an element, if
present, is in the range of about 0.05 to about 2.5 weight percent
based on the weight of said catalyst/absorbing composition and the
concentration of tungsten as an individual promoter, expressed as
an element, if present, is in the range of about 0.4 to about 16
weight percent based on the weight of said catalyst/absorbing
composition.
17. A process in accordance with claim 16 wherein the total
concentration of any combination of said at least one promoter and
said at least one oxidation promoter, expressed as an element, is
in the range of about 1 to about 28 weight percent based on the
weight of said catalyst/absorbing composition.
18. A process in accordance with claim 1 wherein said suitable
hydrodesulfurization conditions comprise a temperature in the range
of about 205.degree. C. to about 538.degree. C., a total system
pressure in the range of about atmospheric to about 1000 psig, a
hydrogen flow rate in the range of about 100 to about 10,000
SCF/bbl and a residence time for said fluid stream in the presence
of said catalyst/absorbing composition in the range of about 0.1 to
about 50 liquid volumes of said fluid stream per volume of said
catalyst/absorbing composition per hour.
19. A process in accordance with claim 1 wherein said suitable
hydrodesulfurization conditions comprise a temperature in the range
of about 260.degree. C. to about 427.degree. C., a total system
pressure in the range of about 15 psig to about 200 psig, a
hydrogen flow rate in the range of about 250 SCF/bbl to about 3,000
SCF/bbl and a residence time for said fluid stream in the presence
of said catalyst/absorbing composition in the range of about 1 to
about 20 liquid volumes of said fluid stream per volume of said
catalyst/absorbing composition per hour.
20. A process in accordance with claim 1 wherein said
catalyst/absorbing composition is sulfided during said
hydrodesulfurization process.
21. A process in accordance with claim 20 additionally comprising
steps of:
discontinuing the flow of said fluid stream over said
catalyst/absorbing composition; and
contacting said catalyst/absorbing composition, after the flow of
said fluid stream is discontinued, with a molecular
oxygen-containing fluid under suitable regeneration conditions to
thereby regenerate said catalyst/absorbing composition.
22. A process in accordance with claim 21 wherein said suitable
regeneration conditions comprise a feed rate of said molecular
oxygen-containing fluid suitable to supply sufficient oxygen to
remove substantially all of the sulfur from said catalyst/absorbing
composition, a temperature in the range of about 370.degree. to
about 815.degree. C., and a pressure in the range of about
atmospheric to about 1000 psig.
23. A process in accordance with claim 22 wherein sulfur is removed
as an oxide during said regeneration period.
24. A process in accordance with claim 21 additionally comprising
the step of purging said catalyst/absorbing composition with an
inert fluid after the step of terminating the flow of said fluid
stream and before the step of regenerating said catalyst/absorbing
composition.
25. A process in accordance with claim 21 additionally comprising
the steps of:
terminating the flow of said molecular oxygen-containing fluid over
said catalyst/absorbing composition after said catalyst/absorbing
composition is regenerated;
purging said catalyst/aborbing composition with an inert fluid
after the flow of said molecular oxygen-containing fluid is
terminated;
terminating the flow of said inert fluid over said
catalyst/absorbing composition after said molecular
oxygen-containing fluid is substantially purged from said
catalyst/absorbing composition; and
recontacting said catalyst/absorbing composition with said fluid
stream after the flow of said inert fluid over said
catalyst/absorbing composition is terminated.
26. A process for hydrodesulfurizing an organic sulfur compound
contained in a fluid stream, which does not contain hydrocarbons
which are subject to dehydrogenation, reforming or hydrocracking,
to convert the sulfur in the organic sulfur compound to hydrogen
sulfide and for removing hydrogen sulfide from the fluid stream
comprising the step of contacting said fluid stream under suitable
hydrodesulfurization conditions with an incompletely sulfided
catalyst/absorbing composition comprising zinc titanate.
27. A process in accordance with claim 26 wherein said organic
sulfur compound is selected from the group consisting of sulfides,
disulfides, mercaptans, carbonyl sulfides, thiophenes,
benzothiophenes, dibenzothiophenes and mixtures of any two or more
thereof.
28. A process in accordance with claim 26 wherein said zinc
titanate is prepared by calcining a mixture of zinc oxide and
titanium dioxide in the presence of molecular oxygen at a
temperature in the range of about 650.degree. C. to about
1050.degree. C.
29. A process in accordance with claim 28 wherein the atomic ratio
of zinc to titanium in said catalyst/absorbing composition is in
the range of about 1:1 to about 3:1.
30. A process in accordance with claim 28 wherein the atomic ratio
of zinc to titanium in said catalyst/absorbing composition is in
the range of about 1.8:1 to about 2.2:1.
31. A process in accordance with claim 26 wherein said suitable
hydrodesulfurization conditions comprise a temperature in the range
of about 205.degree. C. to about 538.degree. C., a total system
pressure in the range of about atmospheric to about 1000 psig, a
hydrogen flow rate in the range of about 100 to about 10,000
SCF/bbl and a residence time for said fluid stream in the presence
of said catalyst/absorbing composition in the range of about 0.1 to
about 50 liquid volumes of said fluid stream per volume of said
catalyst/absorbing composition per hour.
32. A process in accordance with claim 26 wherein said suitable
hydrodesulfurization conditions comprise a temperature in the range
of about 260.degree. C. to about 427.degree. C., a total system
pressure in the range of about 15 psig to about 200 psig, a
hydrogen flow rate in the range of about 250 SCF/bbl to about 3,000
SCF/bbl and a residence time for said fluid stream in the presence
of said catalyst/absorbing composition in the range of about 1 to
about 20 liquid volumes of said fluid stream per volume of said
catalyst/absorbing composition per hour.
33. A process in accordance with claim 26 wherein said
catalyst/absorbing composition is sulfided during said
hydrodesulfurization process.
34. A process in accordance with claim 33 additionally comprising
the steps of:
discontinuing the flow of said fluid stream over said
catalyst/absorbing composition; and
contacting said catalyst/absorbing composition, after the flow of
said fluid stream is discontinued, with a molecular
oxygen-containing fluid under suitable regeneration conditions to
thereby regenerate said catalyst/absorbing composition.
35. A process in accordance with claim 34 wherein said suitable
regeneration conditions comprise a feed rate of said molecular
oxygen-containing fluid suitable to supply sufficient oxygen to
remove substantially all of the sulfur from said catalyst/absorbing
composition, a temperature in the range of about 370.degree. C. to
about 815.degree. C., and a pressure in the range of about
atmospheric to about 1000 psig.
36. A process in accordance with claim 34 wherein sulfur is removed
as an oxide during the regeneration period.
37. A process in accordance with claim 34 additionally comprising
the step of purging said catalyst/absorbing composition with an
inert fluid after the step of terminating the flow of said fluid
stream and before the step of regenerating said catalyst/absorbing
composition.
38. A process in accordance with claim 34 additionally comprising
the steps of:
terminating the flow of said molecular oxygen-containing fluid over
said catalyst/absorbing composition after said catalyst/absorbing
composition is regenerated;
purging said catalyst/absorbing composition with an inert fluid
after the flow of said molecular oxygen-containing fluid is
terminated;
terminating the flow of said inert fluid over said
catalyst/absorbing composition after said molecular
oxygen-containing fluid is substantially purged from said
catalyst/absorbing composition; and
recontacting said catalyst/absorbing composition with said fluid
stream after the flow of said inert fluid over said
catalyst/absorbing composition is terminated.
Description
This invention relates to an improved process for removing sulfur
from fluid streams and/or hydrogenating olefins contained in the
fluid streams. In one aspect this invention relates to an improved
process for selectively removing hydrogen sulfide from fluid
streams. In another aspect this invention relates to an improved
process for hydrodesulfurizing (HDS) organic sulfur compounds
contained in a fluid stream to convert the sulfur in the organic
sulfur compounds to hydrogen sulfide and for removing the thus
produced hydrogen sulfide, and any other hydrogen sulfide present
in the fluid stream, from the fluid stream. In still another aspect
this invention relates to a process for hydrogenating olefins to
paraffins to improve the odor of a fluid containing the
olefins.
Removal of sulfur from fluid streams can be desirable or necessary
for a variety of reasons. If the fluid stream is to be burned as a
fuel, removal of sulfur from the fluid stream can be necessary to
prevent environmental pollution. If the fluid stream is to be
processed, removal of the sulfur is often necessary to prevent
poisoning of sulfur-sensitive catalysts or to satisfy other process
requirements.
A variety of methods are available to remove sulfur from a fluid
stream if the sulfur is present as hydrogen sulfide. These methods
include using alkaline reagents that unselectively absorb all acid
gases. Other methods include the use of selective solid adsorbents
such as zinc oxide and bog iron ore. However, in general these
solid adsorbents are not regenerable to their original form and
must be discarded when they have become completely sulfided.
It is thus an object of this invention to provide an improved
process for selectively removing hydrogen sulfide from fluid
streams. It is a further object of this invention to provide an
improved removal or absorbing composition which possesses the
property of being regenerable to the original absorbing composition
state in the presence of oxygen.
If the sulfur is present in the fluid stream in the form of an
organic sulfur compound, the organic sulfur compound may be
hydrodesulfurized to convert the sulfur in the organic sulfur
compound to hydrogen sulfide which can be removed from the fluid
stream by an absorbing composition.
It is thus another object of this invention to provide a process
for not only removing hydrogen sulfide from a fluid stream but also
hydrodesulfurizing organic sulfur comounds to convert the sulfur in
the organic sulfur compounds to hydrogen sulfide which can then be
selectively removed from the fluid stream.
The presence of olefin contaminants in a fluid may result in a foul
odor associated with the fluid. Also, the olefin contaminants may
be oxidized to even more malodorous products when released into the
air. This is particularly the case in aerosol propellants. It is
thus another object of this invention to provide a process for
hydrogenating olefin contaminants in a fluid and particularly in
aerosol propellants.
In accordance with the present invention, an absorbing composition
comprising zinc, titanium and a promoter is utilized to selectively
remove hydrogen sulfide, if present, from a fluid stream. The
promoter is at least one member selected from the group consisting
of vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum,
rhenium and compounds thereof. The absorbing composition can be
formed by combining zinc oxide and titanium dioxide by any of the
methods known in the art to form zinc titanate. The promoter can
then be added to the zinc titanate. Once the absorbing composition
has been prepared, fluid streams are contacted with the absorbing
composition under suitable absorbing conditions to substantially
reduce the concentration of hydrogen sulfide in the fluid
stream.
The absorbing composition also acts as a hydrodesulfurization
catalyst if organic sulfur compounds are present in the fluid
stream. Under suitable hydrodesulfurization conditions the organic
sulfur compounds are converted to hydrogen sulfide in the presence
of the absorbing composition which acts as a hydrodesulfurization
catalyst. After conversion to hydrogen sulfide, the sulfur will be
removed from the fluid stream by the absorbing composition.
The absorbing composition also acts as an olefin hydrogenation
catalyst if olefin contaminants are present in the fluid stream.
Under suitable olefin hydrogenation conditions the olefin
contaminants are hydrogenated to paraffins in the presence of the
absorbing composition which acts as an olefin hydrogenation
catalyst. The paraffins do not have the undesirable odor and are
not readily oxidized to malodorous products when released into the
air.
It is believed that the hydrogen sulfide is being absorbed by the
absorbing composition and thus the terms "absorption process" and
"absorbing composition" are utilized for the sake of convenience.
However, the exact chemical phenomenon occurring is not the
inventive feature of the process of the present invention and the
use of the term "absorb" in any form is not intended to limit the
present invention.
Hereinafter, the process of the present invention is referred to by
a plurality of terms depending on the reactions occurring. Terms
utilized include selective absorption or absorption process,
hydrodesulfurization process, olefin hydrogenation process and
combinations thereof. The term "absorbing composition" is utilized
to refer to the promoted zinc titanate in general although the term
"catalyst/absorbing composition" is also utilized in some cases
where the promoted zinc titanate is acting as a
hydrodesulfurization catalyst, as a hydrogenation catalyst and/or
as an absorbing composition.
The selective absorption process is preferably carried out in
cycles comprising an absorption period and a regeneration period
for the absorbing composition. The absorption period comprises
contacting a fluid stream containing hydrogen sulfide with the
absorbing composition to thereby selectively remove hydrogen
sulfide from the fluid stream. The absorbing composition becomes
sulfided during the absorption period. When the absorbing
composition becomes sulfided to the point that regeneration is
desirable, preferably when it is substantially completely sulfided,
a gas containing molecular oxygen is passed in contact with the
absorbing composition to regenerate the absorbing composition and
convert the absorbed sulfur to an oxide.
The hydrodesulfurization/absorption process is also preferably
carried out in cycles comprising a reaction period and a
regeneration period for the catalyst. The reaction period comprises
contacting a fluid stream containing organic sulfur compounds with
the hydrodesulfurization/absorption composition to thereby convert
the sulfur in organic sulfur compounds in the fluid stream to
hydrogen sulfide. The hydrodesulfurization/absorption composition
becomes sulfided during the reaction period. When the composition
becomes substantially completely sulfided, a gas containing
molecular oxygen is passed in contact with the
hydrodesulfurization/absorption composition to regenerate the
composition and to convert the absorbed sulfur to an oxide.
Olefin hydrogenation may be combined with either a selective
absorption process or a hydrodesulfurization/absorption process.
Olefin hydrogenation may also occur when sulfur is not present in
the fluid stream being contacted with the promoted zinc titanate.
In all of these cases the process is still carried out in cycles
comprising a reaction period and a regeneration period. It is,
however, noted that, if sulfur is not present in the fluid stream,
the length of the reaction period is determined by coke buildup on
the catalyst.
If desired, at least one oxidation promoter selected from the group
consisting of ruthenium, rhodium, palladium, silver, tungsten,
iridium, platinum, and compounds thereof may also be present to
promote the regeneration of the absorbing composition.
The chemical changes that are believed to occur in the absorbing
composition during this cyclic process where sulfur is present are
summarized in the following equations:
Other objects and advantages of the invention will be apparent from
the foregoing description of the invention and the appended claims
as well as from the detailed description of the invention which
follows.
Any suitable organic sulfur compound may be hydrodesulfurized in
accordance with the present invention. Suitable organic sulfur
compounds include sulfides, disulfides, mercaptans, carbonyl
sulfides, thiophenes, benzothiophenes, dibenzothiophenes and
mixtures of any two or more thereof.
The absorbing composition of the present invention may be utilized
to remove hydrogen sulfide from any suitable fluid stream. The
hydrogen sulfide may be produced by the hydrodesulfurization of
organic sulfur compounds or may be originally present in the fluid
stream as hydrogen sulfide. Suitable fluid streams include light
hydrocarbons such as methane, ethane and natural gas, petroleum
products and products from extraction and/or liquefaction of coal
and lignite, products from tar sands, products from shale oil, coal
derived synthesis gas, gases such as hydrogen and nitrogen, gaseous
oxides of carbon, steam, and the inert gases such as helium and
argon. Gases that adversely affect the removal of hydrogen sulfide
and which should be absent from the fluid streams being processed
are oxidizing agents such as molecular oxygen, the halogens, the
oxides of nitrogen, and the like.
The absorbing composition of the present invention may be utilized
to remove hydrogen sulfide from olefins such as ethylene. However,
this process should be carried out in the absence of free hydrogen
to avoid hydrogenation. Olefin streams should not be
hydrodesulfurized as this may result in undesirable hydrogenation
of at least a portion of the olefins to paraffins.
The absorbing composition of the present invention may be utilized
to hydrogenate olefin contaminants in any suitable fluid stream. It
is particularly desirable to remove olefin contaminants from
C.sub.3 and C.sub.4 paraffins such as isobutane, n-butane and
propane which are utilized as aerosol propellants. The present
invention is particularly directed to hydrogenating light olefins
such as ethylene, propylene, n-butenes, isobutene, n-pentenes and
branched pentenes contained in aerosol propellants.
The absorbing composition employed in the process of the present
invention is a composition consisting essentially of zinc, titanium
and a promoter. The promoter is at least one member selected from
the group consisting of vanadium, chromium, manganese, iron,
cobalt, nickel, molybdenum, rhenium, and compounds thereof. At
least one oxidation promoter selected from the group consisting of
ruthenium, rhodium, palladium, silver, tungsten, iridium, platinum,
and compounds thereof, may also be present in the absorbing
composition. The zinc and titanium are generally present in the
absorbing composition as zinc titanate. The promoters may be
present in the absorbing composition as oxides, sulfides or as the
free element. A preferred combination of promoters is cobalt oxide
plus molybdenum oxide where the cobalt:molybdenum atomic ratio is
in the range of 0.3:1 to about 0.8:1.
The zinc titanate base of the absorbing composition may be prepared
by intimately mixing suitable portions of zinc oxide and titanium
dioxide, preferably in a liquid such as water, and calcining the
mixture in a gas containing molecular oxygen at a temperature in
the range of about 650.degree. C. to about 1050.degree. C.,
preferably in the range of about 675.degree. C. to about
975.degree. C. A calcining temperature in the range of about
800.degree. C. to about 850.degree. C. is most preferred because
the surface area of the catalyst is maximized in this temperature
range thus producing a more active catalyst. The titanium dioxide
used in preparing the zinc titanate preferably has extremely fine
particle size to promote intimate mixing of the zinc oxide and
titanium dioxide. This produces a rapid reaction of the zinc oxide
and titanium dioxide which results in a more active catalyst.
Preferably the titanium dioxide has an average particle size of
less than 100 millimicrons and more preferably less than 30
millimicrons. Flame hydrolyzed titanium dioxide has extremely small
particle size and is particularly preferred in preparing the
catalyst. The atomic ratio of zinc to titanium can be any suitable
ratio. The atomic ratio of zinc to titanium will generally lie in
the range of about 1:1 to about 3:1 and will preferably lie in the
range of about 1.8:1 to about 2.2:1 because the activity of the
absorbing composition is greatest for atomic ratios of zinc to
titanium in this preferred range. The term "zinc titanate" is used
regardless of the atomic ratio of zinc to titanium.
The zinc titanate base of the absorbing composition may also be
prepared by coprecipitation from aqueous solutions of a zinc
compound and a titanium compound. The aqueous solutions are mixed
together and the hydroxides are precipitated by the addition of
ammonium hydroxide. The precipitate is then washed, dried and
calcined as described in the preceding paragraph. This method of
preparation is less preferred than the mixing method because the
zinc titanate prepared by the coprecipitation method is softer than
the zinc titanate prepared by the mixing method.
The promoter, at least one member of which is selected from the
group consisting of vanadium, chromium, manganese, iron, cobalt,
nickel, molybdenum, rhenium, and compounds thereof, is generally
present in the absorbing composition in the oxide form. The
oxidation promoter, at least one member of which is selected from
the group consisting of ruthenium, rhodium, palladium, silver,
tungsten, iridium, platinum, and compounds thereof will generally
be present in the absorbing composition as the free metal or the
oxide form if utilized. The promoter or combination of promoters
can be added to the zinc titanate by any method known in the art.
The promoter or combination of promoters can be added to the zinc
titanate as pwodered oxide and dispersed by any method known in the
art such as rolling, shaking or stirring. The preferred method of
adding the promoter is by impregnating the preformed zinc titanate
with a solution of a compound of the promoting element. After
impregnation, the absorbing composition is preferably dried to
remove solvent and is then heated in air at a temperature in the
range of about 500.degree. to about 650.degree. C., preferably
about 540.degree. C., before being utilized for the absorption
process of hydrodesulfurization/absorption process. If more than
one promoter is to be used, the absorbing composition is preferably
dried and calcined after each promoter addition.
The concentration of the promoter in the absorbing composition may
be any suitable concentration. The concentration of vanadium,
chromium, manganese, iron, cobalt, nickel, or molybdenum expressed
as an element, if present, will generally be in the range of about
0.4 to 16 weight percent based on the weight of the promoted
absorbing composition. A combination of these promoters may be
utilized. However, the total concentration of the promoters,
expressed as an element, should be in the range of about 1 to about
28 weight percent based on the weight of the promoted absorbing
composition. The concentration of rhenium, expressed as an element,
will generally be in the range of about 0.05 to about 2.5 weight
percent based on the weight of the promoted absorbing composition.
The rhenium may also be utilized in combination with the vanadium,
chromium, manganese, iron, cobalt, nickel, and molybdenum but again
the total concentration of the promoters, expressed as an element
should not exceed 28 weight percent based on the weight of the
promoted absorbing composition. The concentration of ruthenium,
rhodium, palladium, silver, iridium or platinum, expressed as an
element, if present, will generally be in the range of about 0.05
to about 2.5 weight percent based on the weight of the promoted
absorbing composition. The concentration of tungsten, expressed as
an element, if present, will generally be in the range of about 0.4
to about 16 weight percent based on the weight of the promoted
absorbing composition. The oxidation promoters, if utilized, are
always utilized in combination with the promoters, at least one
member of which is selected from the group consisting of vanadium,
chromium, manganese, iron, cobalt, nickel, molybdenum, rhenium, and
compounds thereof. Again, the total concentration of the promoters,
including the oxidation promoters, should not exceed 28 weight
percent based on the weight of the promoted absorbing
composition.
Either the elemental form of the promoters or any suitable compound
of the promoters may be used to form the absorbing composition.
Suitable compounds of the promoting elements that can be applied to
zinc titanate by solution impregnation include the nitrates,
sulfates, acetates and the like of chromium, manganese, iron,
cobalt, nickel, and silver; ammonium salts of vanadates,
molybdates, tungstates, rhenates and perrhenates; and nitrates,
chlorides, or hexachloro ammonium salts of ruthenium, rhodium,
palladium; and dihydrogen hexachloroplatinate.
The processes of the present invention can be carried out by means
of any apparatus whereby there is achieved an alternate contact of
the absorbing composition with the fluid stream and thereafter of
the absorbing composition with a fluid containing molecular oxygen
utilized to regenerate the absorbing composition. The process is in
no way limited to the use of a particular apparatus. The process of
this invention can be carried out using a fixed absorbing
composition bed, fluidized absorbing composition bed or moving
absorbing composition bed. Presently preferred is a fixded
absorbing composition bed.
In order to avoid any casual mixing of the fluid stream which
contains organic sulfur compounds, olefin contaminants and/or
hydrogen sulfide with the oxygen-containing fluid utilized in the
regeneration step, provision is preferably made for terminating the
flow of the fluid stream to the reactor and subsequently injecting
an inert purging fluid such as nitrogen, carbon dioxide or steam.
Any suitable purge time can be utilized but the purge should be
continued until all hydrocarbon and/or hydrogen are removed. Any
suitable flow rate of the purge fluid may be utilized. Presently
preferred is a purge fluid flow rate in the range of about 800 GHSV
to about 1200 GHSV.
Any suitable temperature of the processes of the present invention
may be utilized. For both absorption and olefin hydrogenation the
temperature will generally be in the range of about 149.degree. C.
to about 538.degree. C. and will more preferably be in the range of
about 204.degree. C. to about 399.degree. C. For
hydrodesulfurization the temperature will generally be in the range
of about 205.degree. C. to about 538.degree. C. and will more
preferably be in the range of about 260.degree. C. to about
427.degree. C.
Any suitable temperature may be utilized to regenerate the
absorbing composition from its sulfided form back to the original
absorbing composition form or to simply burn off carbon if only
olefin hydrogenation is occurring. The temperature will generally
be in the range of about 370.degree. C. to about 815.degree. C. A
temperature of at least 540.degree. C. is preferred to effect the
conversion within a reasonable time.
Any suitable pressure for the processes of the present invention
can be utilized. For hydrodesulfurization the pressure will range
of from about atmospheric to about 1,000 psig. This pressure is the
sum of the partial pressure of the fluid stream plus the partial
pressure of the added hydrogen. Preferably, the pressure will be in
the range of from about 15 psig to about 200 psig with about 80
psig being particularly preferred for economy of operation as a
cyclic process. The low pressure at which the hydrodesulfurization
can be accomplished is a particularly advantageous feature of the
present invention.
For olefin hydrogenation the pressure will range from about 100
psig to about 1000 psig with a pressure in the range of about 100
psig to about 500 psig being preferred. Again the pressure is the
sum of the partial pressure of the fluid stream plus the partial
pressure of the added hydrogen.
The pressure of the fluid stream being treated is not believed to
have an important effect on the absorption process of the present
invention. The pressure will be in the range of from about
atmospheric to at least 2,000 psig during the treatment.
Any suitable quantity of hydrogen can be added to accomplish the
hydrodesulfurization and/or olefin hydrogenation. The quantity of
hydrogen used to contact the fluid stream containing the organic
sulfur compounds being hydrodesulfurized will generally be in the
range of about 100 to about 10,000 SCF/bbl and will more preferably
be in the range of about 250 to about 3,000 SCF/bbl. For olefin
hydrogenation, the hydrogen concentration should be at least
sufficient to hydrogenate all olefins, i.e., mole percent hydrogen
added should equal mole percent olefins. Preferably, the mole
percent hydrogen will be 2-3 times the mole percent of olefins. The
presence of additional hydrogen is not required for the absorption
process.
Any suitable residence time for the fluid stream in the presence of
the absorbing composition of the present invention can be utilized.
Where the fluid stream is a liquid, the residence time in terms of
the volumes of liquid per volume of absorbing composition per hour
will generally be in the range of about 0.1 to about 50 and will
more preferably be in the range of about 1 to about 20. Where the
fluid stream is a gaseous stream, the residence time expressed as
volumes of gas at standard temperature and pressure per volume of
absorbing composition per hour will generally be in the range of
about 10 to about 10,000 and will more preferably be in the range
of about 250 to about 2500.
The absorbing composition of the present invention continues to be
effective for converting organic sulfur compounds to hydrogen
sulfide or hydrogenating olefin contaminants even when completely
sulfided. However, when the absorbing composition is completely
sulfided it will no longer combine with the hydrogen sulfide in the
manner set forth in equation (I). When this condition occurs,
hydrogen sulfide will begin to appear in the effluent flowing from
the reaction and this will be an indication that the absorbing
composition should preferably be regenerated. The time required for
the absorbing composition to become completely sulfided will
generally be a function of the concentration of sulfur in the
feedstock and feed rate employed.
When the absorbing composition becomes substantially completely
sulfided, the absorbing composition is typically regenerated by
terminating the flow of feed to the reactor and purging with an
inert fluid such as nitrogen to remove any combustibles. A free
oxygencontaining fluid is then introduced to oxidize the zinc
sulfide in accordance with equation (II). Also at the temperature
at which the oxidation of the zinc sulfide is effected, the zinc
oxide thus produced recombines with the titanium dioxide to
resynthesize the original zinc titanate in accordance with equation
(III).
If only olefin hydrogenation is occurring, the regeneration step
may be utilized to remove coke from the promoted zinc titanate when
the catalyst becomes fouled. If absorption is occurring, the
promoted zinc titanate will generally become completely sulfided
long before the formation of coke becomes a problem. Thus,
sulfiding of the catalyst generally determines the length of the
reaction period if absorption is occurring.
If absorption is occurring, the amount of oxygen, from any source,
supplied during the regeneration step will generally be in an
amount sufficient to at least substantially remove sulfur from the
absorbing composition. The regeneration step is conducted at
generally about atmospheric pressure. The temperature for the
regeneration step is preferably maintained in the range of about
370.degree. to about 815.degree. C. and is more preferably
maintained at about 540.degree. C. in order to both oxidize the
zinc sulfide and convert the zinc oxide and titanium dioxide to
zinc titanate within a reasonable time. If absorption is not
occurring, the amount of oxygen, from any source, supplied during
the regeneration step will be at least the amount sufficient to
remove substantially all carbonaceous materials from the promoted
zinc titanate.
Examination of absorbing composition from various stages of the
cyclic process confirms the suppositions made by observing reaction
products from process studies. Zinc titanate promoted with about 18
weight percent of cobalt and molybdenum oxides shows an X-ray
diffraction pattern of only the Zn.sub.2 TiO.sub.4. When completely
sulfided, the X-ray diffraction pattern becomes zinc sulfide (both
wurtzite and sphalerite) and titanium dioxide (anatase only). After
regeneration with air, the absorbing composition again has an X-ray
diffraction pattern identical with that of the original material
except for the occasional observation of traces of zinc molybdate.
Presumably, both the cobalt and molybdenum follow the zinc in being
oxides or sulfides. It has been noted that repetitive operation
through these cycles causes a significant increase in the surface
area of the zinc titanate absorbing composition. The surface area
of the zinc titanate absorbing composition is higher in the
sulfided form than in the oxidized form. Reformation of zinc
titanate in this process occurs at a temperature significantly
lower than that required to synthesize the material when starting
with the pure oxides.
The following examples are presented in further illustration of the
invention.
EXAMPLE 1
Zinc titanate having an atomic ratio of Zn:Ti=2.0:1 was prepared by
mixing 162.8 g (2 moles) of Mallinckrodt zinc oxide with 79.9 g
(one mole) of Cab-O-Ti titanium dioxide (flame hydrolyzed) in 1200
mL of water in a blender for 10 minutes. The resulting slurry was
oven dried at 105.degree. C. and then calcined in air for 3 hours
at 816.degree. C. After cooling, the thus calcined material was
crushed and screened. Portions of the screened zinc titanate having
the size set forth in Table I were modified by the addition of
various promoters to produce absorbing compositions A-G.
The general method for preparing each absorbing composition was as
follows. A weighed portion of zinc titanate, prepared as previously
described, having a known pore volume was covered with a solution
(generally aqueous) of known concentration of the promoting
element. After standing one hour at 25.degree. C., excess solution
was removed by decanting or filtering and the wet catalyst was
dried, with occasional stirring, in an oven, on a hot plate, or
under a heat lamp. The dried catalyst was calcined in air in a
muffle furnace for 3-4 hours at 538.degree. C., cooled in a
desiccator, and reweighed. The quantity of promoter added by this
procedure was considered to be calculable from the volume of
promoter solution contained in the pores of the zinc titanate.
Occasionally, this quantity was checked by observing the gain in
weight of the absorbing composition made as described, but this
gain was not considered to provide a definitive value of
concentration. To add more than one promoter, the entire procedure
described here was repeated for each impregnation.
The concentration of the promoter in the solution used to
impregnate the zinc titanate to a desired level was calculated from
the formula ##EQU1## where n=number of atoms of promoter element
per molecule of compound. To illustrate, to prepare an absorbing
composition containing 8.0 weight percent molybdenum on zinc
titanate that has 0.8 mL/g pore volume, using ammonium
heptamolybdate tetrahydrate as the source of molybdenum.
##EQU2##
The composition, size, and surface area of absorbing compositions
A-G are summarized in Table I. In every case zinc titanate
comprised the unreported portion of the absorbing composition.
TABLE I ______________________________________ Size, Surface
Absorbing U. S. Area Compositions Promoters, Wt. % Sieve m.sup.2 /g
______________________________________ A 6.4 CoO, 11.3 MoO.sub.3,
0.1 Pt -8 + 14 3.0 B 0.2 CoO, 0.65 MoO.sub.3 -16 + 40 5.8 C 2.8
CoO, 5.0 MoO.sub.3 -16 + 40 5.9 D 4.0 NiO, 13.0 MoO.sub.3 -16 + 40
4.3 E 7.6 NiO, 24 WO.sub.3 -16 + 40 5.8 F 2.6Re.sub.2 O.sub.7 -16 +
40 6.0 G 13.0 MoO.sub.3 -16 + 40 5.1
______________________________________
The promoters were added as aqueous solutions of the following
salts. Cobalt as Co(NO.sub.3).sub.2.6H.sub.2 O, molybdenum as
(NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O, platinum as H.sub.2
PtCl.sub.6.6H.sub.2 O, nickel as Ni(NO.sub.3).sub.2.6H.sub.2 O,
tungsten as (NH.sub.4).sub.2 W.sub.4 O.sub.13.8H.sub.2 O, and
rhenium as NH.sub.4 ReO.sub.4.
Absorbing composition A from Table I was used in a cyclic manner
for hydrodesulfurization (HDS). A complete process cycle consisted
of
(1) Hydrotreating 2.75 weight percent thiophene in cyclohexane (1.0
wt. % organic sulfur) at 160 psig pressure for 120 minutes between
370.degree.-427.degree. C. using 3.0 LHSV and adding about 0.5 mole
hydrogen per mole of liquid feed,
(2) Terminating the flow of feed,
(3) Purging with nitrogen for 30 minutes while temperature is
increased to about 566.degree. C.,
(4) Regenerating the thus purged absorbing composition A with air
for 120 minutes at 566.degree. C.,
(5) Terminating the flow of the air,
(6) Purging with nitrogen for 30 minutes while temperature cools to
about 370.degree. C.,
(7) Purging with hydrogen for 30 minutes at 370.degree.-427.degree.
C. and then introducing feed per step (1). Steps 3, 4, 6 and 7 were
all made at pressures between 0-30 psig.
Results obtained through 95 cycles of operation are summarized in
Table II.
TABLE II ______________________________________ HDS wt. % of sulfur
originally Cyclohexane Cycle No. HDS Temp., .degree.C. present
Loss, % ______________________________________ 10 432 99 3 27 381
84 0 72 377 94 0 87 387 82 0 88-95 comp. 388 >90 0
______________________________________
During each 120 minute process cycle, 10.5 weight percent of the
original sulfur required to completely sulfide the absorbing
composition was introduced into the reactor. (It is believed that
cobalt and molybdenum, in addition to the zinc, become sulfided.)
Table II shows that hydrodesulfurization activity was sustained
during the 95 cycles that absorbing composition A was used.
Absorbing compositions B through G were used in
hydrodesulfurization/absorption runs that demonstrate the
hydrodesulfurization/absorption process. Table III, which describes
the feedstock and summarizes run conditions, shows that all of
these absorbing compositions were active to hydrodesulfurize
organic sulfur compounds, and frequently the absorbing composition
activity improved with use. Table III also shows that after use the
absorbing composition contained approximately the stoichiometric
concentration of sulfur. (For reference unpromoted Zn.sub.2
TiO.sub.4 in which the zinc has been completely sulfided contains
23.34 weight percent sulfur.) After regeneration the concentration
of sulfur was substantially reduced. X-ray diffraction analysis
indicates that the sulfur was retained in the sulfide form, not as
sulfate. X-ray diffraction showed also that the predominant
crystalline components of used absorbing compositions were zinc
sulfide and titanium dioxide. After regeneration, zinc titanate was
the principal crystalline component. Table III also shows the
surface area of the sulfided catalyst to be substantially larger
than that of the regenerated form of the absorbing
compositions.
TABLE III
__________________________________________________________________________
HDS wt % of sulfur Absorbing Composition Absorbing No. of
originally Absorbing Composition After HDS After Regen.sup.(3)
Compositions Regen. present.sup.(1) Wt. % S Wt. % C SA, m.sup.2 /g
XRD.sup.(2) Wt. % S SA, m.sup.2 /g XRD.sup.(2)
__________________________________________________________________________
B Fresh 85.3 20.3 0.56 22.5 ZnS, TiO.sub.2, 0.80 5.3 ZT,trZnO, 1
84.0 22.4 0.60 19.5 trZT ND ND trZns 2 88.0 23.6 0.82 ND 1.0 5.6 C
Fresh 92.5 21.8 0.46 13.3 ZnS,TiO.sub.2, 1.28 6.6 ZT 1 98.9 27.8
0.83 21.1 trZT 2.0 8.5 2 98.9 20.6 1.01 20.1 3.1 5.9 D Fresh 93.9
25.1 0.36 ND ZnS,TiO.sub. 2, 4.45 8.2 ZT,ZnS,trZnO, 1 98.7 22.6
0.83 17.6 Ni.sub.3 S.sub.2 MoS.sub.2 3.93 7.0 trTiO.sub.2,trZnMoO.
sub.4 E Fresh 94.7 15.2 0.39 ND ZnS,TiO.sub.2 8.34 ND ZT,ZnS, ZnO 1
90.9 15.9 0.29 8.2 ZT,ZnWO.sub.4 7.2 TiO.sub.2,InWO.sub.4 -F Fresh
80.5 20.8 0.36 14.9 ZnS,TiO.su b.2 4.86 9.6 ZT,trTi O.sub.2, 1 92.3
22.0 0.55 25.0 ND ND G Fresh 87.5 22.6 0.47 ND ZnS,TiO.sub.2 1.37
ND ZT,ZnMoO.sub.4
__________________________________________________________________________
.sup.(1) Tested at 399.degree. C., 500 psig, 1.0 LHSV using
feedstock fro 70% straight run distillate plus 30% 105-388.degree.
C. light cycle oil (0.75 wt. % organic S in blend); 9.5 moles
hydrogen per mole liquid feed; runs 24-60 hr. duration. .sup.(2)
ZnS:wurtzite plus sphalerite; TiO.sub.2 :anatase only; Zt:zinc
titanate; tr:trace .sup.(3) Absorbing composition was regenerated
for 2 hours at 538.degree. C. in air in a muffle furnace.
EXAMPLE 2
Direct comparisons of hydrodesulfurization activity were made
between zinc oxide and zinc titanate where both were unpromoted,
where both were promoted with molybdenum oxide only, and where both
were promoted with cobalt molybdate. All runs were made over a
range of temperatures at 1.0 LHSV, 500 psig reactor pressure with
5000 SCF hydrogen per barrel of feed. The feedstock was a
104.degree.-388.degree. C. boiling range distillate that contained
0.73 wt. % organic sulfur. Girdler G-720 zinc oxide (a commercial
desulfurization catalyst) and zinc titanate synthesized as
described in Example 1 were used to make these runs. Promoters were
added to the zinc oxide and zinc titanate using the method
described in Example 1. In all cases the absorbing compositions
were--20+40 mesh U.S. sieve fraction. All catalysts were
regenerated in air for two hours at 538.degree. C.
Results from runs with unpromoted zinc oxide and zinc titanate are
summarized in Table IV.
TABLE IV ______________________________________ Absorbing
Composition ZnO Zn.sub.2 TiO.sub.4 Fresh Regen. Fresh Regen.
______________________________________ Surface area, m.sup.2 /g
10.5 10.5 7.6 7.6 HDS, wt % of sulfur originally present:
650.degree. F. 40.0 22.7 28.0 33.3 700 49.3 29.3 46.7 43.3 750 45.3
42.7 54.7 60.0 775 53.3 52.0 66.7 70.7 Absorbing Composition
Inspection: Carbon, wt. % 0.34 0.28 0.30 0.57 Sulfur, wt. % After
HDS 15.0 18.8 13.3 17.6 After regen. 11.9 11.7 7.1 10.8 XRD
analysis after HDS: ZnO Zn.sub.2 TiO.sub.4 ZnS ZnS TiO.sub.2
(anatase) XRD analysis after regen. ZnO Zn.sub.2 TiO.sub.4 ZnS ZnS
ZnSO.sub.4 TiO.sub.2 (anatase)
______________________________________
Although both absorbing compositions showed significant
hydrodesulfurization activity when fresh, zinc oxide was inferior
at all temperatures after regeneration. In contrast zinc titanate
tended to improve after regeneration. Neither absorbing composition
regenerated well as indicated by their sulfur content.
Results from runs using zinc oxide and zinc titanate promoted only
with molybdenum trioxide are summarized in Table V.
TABLE V ______________________________________ Absorbing
Composition 12.75 wt % 13.2 wt. % MoO.sub.3 /ZnO MoO.sub.3
/Zn.sub.2 TiO.sub.4 Fresh Regen. Fresh Regen.
______________________________________ Surface area, m.sup.2 /g 6.5
N.D. 5.3 7.6 HDS, wt % of sulfur originally present: 650.degree. F.
75.3 34.7 63.9 54.7 700 88.1 48.0 84.7 81.3 750 95.9 65.3 97.6 96.0
775 98.1 72.0 96.1 97.1 Absorbing Composition Inspection: Carbon,
wt. % 0.35 0.27 0.72 0.55 Sulfur, wt. % After HDS 12.0 28.5 20.3
21.3 After regen. 10.8 16.5 0.73 not regen. XRD analysis after HDS:
ZnS ZnS TiO.sub.2 (trace rutile) XRD analysis after ZnS Zn.sub.2
TiO.sub.4 regen. ZnO-trace ZnMoO.sub.4 - trace
______________________________________
Unused zinc oxide promoted with molybdenum trioxide is seen to be
excellent for hydrodesulfurization. After regeneration its
hydrodesulfurization activity has decreased markedly. In contrast,
zinc titanate promoted with molybdenum oxide, while possibly less
active when unused, is seen to be appreciably more active after
regeneration. Sulfur analyses showed that the promoted zinc
titanate gave up a much larger fraction of its sulfur than the
promoted zinc oxide did when regenerated. In addition the promoted
zinc oxide contained enough inactive zinc sulfate (ZnSO.sub.4) to
be seen by X-ray diffraction analysis.
Results from runs using zinc oxide and zinc titanate promoted with
cobalt molybdate are summarized in Table VI.
TABLE VI
__________________________________________________________________________
4.0 wt % CoO- 3.4 wt % CoO- 12.3 wt % MoO.sub.3 /ZnO 14.7 wt %
MoO.sub.3 /Zn.sub.2 TiO.sub.4 Absorbing Composition Fresh Regen.
Fresh Regen.
__________________________________________________________________________
Surface area, m.sup.2 /g N.D.** N.D. 8.6 N.D. HDS, wt % of sulfur
originally present: 650.degree. F. 73.3 78.7 93.3 88.0 700 85.3
86.7 98.7 94.7 750 94.7 92.0 94.7 98.7 775 97.2 94.7 99.6 99.2*
Absorbing Composition Inspection: Carbon, wt. % 0.30 0.30 0.65 0.58
Sulfur, wt. % After HDS 16.8 29.0 24.8 24.2 After regen. 13.3 21.2
1.1 not regen. XRD analysis after HDS: ZnS ZnS ZnMoO.sub.4 -
TiO.sub.2 trace (anatase) XRD analysis after regen.: ZnS
ZnTiO.sub.4 ZnO ZnO-trace ZnMoO.sub.4 ZnMoO.sub.4 -trace ZnSO.sub.4
__________________________________________________________________________
*At 800.degree. F.; not measured at 775.degree. F. **Not determined
but prepared by adding cobalt to the MoO.sub.3 /ZnO
Zinc oxide and zinc titanate are both effective
hydrodesulfurization absorbing compositions when promoted with
cobalt molybdate. However, the promoted zinc titanate was shown to
be superior when fresh and also after regeneration when compared
with the promoted zinc oxide. Again, the sulfur analyses showed
that zinc titanate gave up a much larger fraction of sulfur than
the zinc oxide did upon being regenerated.
EXAMPLE 3
Zinc titanate having an atomic ratio of Zn:Ti=1.8:1 was prepared by
mixing 73.2 g (0.9 moles) of Mallinckrodt zinc oxide with 40.0 g
(0.5 moles) of Cab-O-Ti titanium dioxide (flame hydrolyzed) in 600
cc of water in a blender for 10 minutes. The resulting slurry was
oven dried at 105.degree. C. and then calcined in air for 4 hours
at 815.degree. C. After cooling, the thus calcined material was
crushed and screened. A -10+40 mesh fraction of the screened zinc
titanate was retained to prepare absorbing compositions H and
I.
Absorbing composition H was prepared by soaking 32.2 g of the zinc
titanate in an excess of solution prepared by dissolving 17.42 g of
(NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O and 19.02 g of
Co(NO.sub.3).sub.2.6H.sub.2 O in water containing sufficient
ammonia to completely dissolve the cobalt compound and diluting to
150 mL. Excess solution was removed by filtration. The resulting
residue was dried and calcined in air at 538.degree. C. for one
hour. The resulting solid (absorbing composition H) contained, by
chemical analysis, 2.80 weight percent CoO and 7.95 weight percent
MoO.sub.3, and had a surface area of 5.9 m.sup.2 /g.
Absorbing composition I was prepared by soaking 55 g of the zinc
titanate in an excess of solution containing 17.4 g of
(NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O/100 mL. Excess
solution was removed by filtration. The resulting residue was dried
and calcined in air at 538.degree. C. for one hour. After cooling
the resulting solid was soaked in a solution that contained 20.9 g
of Co(NO.sub.3).sub.2.6H.sub.2 /100 mL. Again excess solution was
removed by filtration. The resulting residue was dried and calcined
in air at 538.degree. C. for one hour. The resulting solid
absorbing composition I contained, by chemical analysis, 5.21
weight percent CoO and 13.35 weight percent MoO.sub.3, and had a
surface area of 6.5 m.sup.2 /g.
Prior to being used as a hydrogen sulfide absorbent, absorbing
composition H was used as a catalyst to hydrodesulfurize a
petroleum fraction. Absorbing composition H was subjected to three
periods of sulfiding followed by oxidative regeneration.
Hydrodesulfurization runs were at 500 psig using temperatures
between 315.degree.-427.degree. C.--conditions equivalent to those
desired for H.sub.2 S adsorption. Regeneration was with air for two
hours at 538.degree. C. The absorption process is illustrated by
the sulfur content of absorbing composition H determined by
chemical analysis of a small, representative sample from each phase
of the operation as is set forth in Table VII.
TABLE VII ______________________________________ Original sample
0.00 wt. % sulfur After 1st HDS run 21.8 wt. % sulfur After 1st
regeneration 1.28 wt. % sulfur After 2nd HDS run 27.8 wt. % sulfur
After 2nd regeneration 3.87 wt. % sulfur After 3rd HDS run 20.6 wt.
% sulfur After 3rd regeneration 3.09 wt. % sulfur
______________________________________
Elemental analysis, weight changes, and X-ray diffraction data of
absorbing composition H after each hydrodesulfurization period and
each regeneration period showed no evidence of formation of
inactive ZnSO.sub.4.
Following the three hydrodesulfurization periods and the three
regeneration periods set forth in Table VII, absorbing composition
H supplemented with 3.75 g of fresh absorbing composition H to
replace the portion of absorbing composition H which had been
expended for chemical analyses to obtain the data set forth in
Table VII, was used in a run to remove hydrogen sulfide from a gas
mixture prepared to simulate natural gas. The gas mixture was a
blend synthesized to contain nominally five mole percent each of
hydrogen sulfide and carbon dioxide in methane. The gas mixture was
passed through a stainless steel tube reactor mounted vertically in
an electrically heated tube furnace at a space rate of 366
hr..sup.-1 for 4.5 hours at 373.degree. C. and atmospheric
pressure. The stainless steel tube contained absorbing composition
H. Analyses of effluent gas made during the run using Drager tubes
(calibrated colorimetric detectors from National Drager, Inc.,
Pittsburgh, PA, and available through laboratory and safety
equipment suppliers) were consistently negative, indicating that
less than 0.04 ppm hydrogen sulfide remained in the gas. Analyses
in triplicate of the feed sample and the effluent product by
gas-liquid chromatography (GLC) for carbon dioxide showed 6.49 and
6.74 mole percent, respectively. These concentrations show that
essentially none of the carbon dioxide was removed from the methane
while no detectable amount of hydrogen sulfide was found in the
effluent. At the conclusion of the run about 41 percent of the zinc
in absorbing composition H had been sulfided.
Prior to being utilized as a hydrogen sulfide adsorbent, absorbing
composition I was used as a catalyst to hydrodesulfurize a
petroleum fraction. Absorbing composition I was subjected to two
periods of hydrodesulfurization with a regeneration period between
the two hydrodesulfurization periods. Hydrodesulfurization runs
were at 500 psig using temperatures between 315.degree. and
427.degree. C. Regeneration was with air for two hours at
538.degree. C. The absorption process is illustrated by the sulfur
content of absorbing composition I determined by chemical analysis
of a small, representative sample from each phase of the operation
as set forth in Table VIII.
TABLE VIII ______________________________________ Original sample
0.00 wt. % sulfur After 1st HDS run 21.0 wt. % sulfur After 1st
regeneration 8.0 wt. % sulfur After 2nd HDS run 23.2 wt. % sulfur
______________________________________
24.26 g of absorbing composition I remained after the analysis was
performed after the second hydrodesulfurization run set forth in
Table VIII. The remaining portion of absorbing composition I was
regenerated in air at 538.degree. C. for two hours and then used,
without being analyzed for sulfur, in a run to remove hydrogen
sulfide from the effluent of an operating hydrodesulfurization
process. The hydrodesulfurization effluent contained, by analysis,
0.49 mole percent hydrogen sulfide. The concentration of the other
components of the hydrodesulfurization effluent was not determined
although the hydrodesulfurization effluent was known to be
principally hydrogen with small amounts of hydrocarbons. Absorbing
composition I was contained in a stainless steel tube reactor which
was mounted vertically in a tube furnace. The hydrodesulfurization
effluent was passed over absorbing composition I at a space rate of
1200 hours.sup.-1 for 5.5 hours at a temperature of 400.degree. C.
and atmospheric pressure. Analysis of the hydrodesulfurization
effluent, after the hydrodesulfurization effluent had been
contacted with absorbing composition I, with Drager tubes was
negative which indicates that the hydrogen sulfide concentration
was less than 0.04 ppm.
The temperature of absorbing composition I was reduced to
204.degree. C. and the hydrodesulfurization effluent was passed
over absorbing composition I in the stainless steel reactor at a
space rate of 1200 hour.sup.-1, for 4 hours at atmospheric
pressure. At the lower temperature of 204.degree. C., about 5 ppm
hydrogen sulfide remained in the hydrodesulfurization effluent
after the hydrodesulfurization effluent had been contacted with
absorbing composition I.
EXAMPLE 4
A catalyst having a composition nearly identical to that of
absorbing composition H, in Example 3, was used to purify isobutane
that was to be used as an aerosol propellant. The catalyst
contained 2.6 wt. % CoO, 8.3 wt. % MoO.sub.3, had 9.8 m.sup.2 /g
surface area and 1.12 g/mL bulk density. Thirty mL of -20+40 mesh
catalyst, loaded into a tubular reactor, was placed in a vertical,
electrically heated, temperature controlled furnace. Isobutane at
17.5 LHSV plus hydrogen at 215 SCF/bbl passed downflow through the
reactor at 300.degree. C. and 1.34 MPa. The isobutane initially
contained 2 parts per million total sulfur and from 20 to 150 parts
per million olefins. After treatment as described, it contained
less than five parts per million olefins as measured by GLC, and
had no sulfur or unpleasant odor.
Reasonable variations and modifications are possible within the
scope of the disclosure and the appended claims to the
invention.
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